1. Technical Field
This invention relates generally to a test fixture for holding a filter exposed to an exhaust gas stream, and more particularly to such a test fixture for collecting particulate matter emitted from an engine during a defined test sequence.
2. Background Art
The U.S. Environmental Protection Agency (EPA) has set very stringent emissions standards for nonroad engines and heavy-duty highway vehicle engines. The standards are directed at reducing smog-causing emissions from stationary engines, off-road vehicles, trucks, buses, recreational vehicles, and motor homes. In particular, standards set forth for model year 2007 limit heavy-duty highway engine particulate matter (PM) emissions to 0.01 g/bhp-hr.
Extensive engine development, testing, and validation will be required to achieve and certify that engines manufactured in 2007, and later, meet the required emissions standards. The U.S. Environmental Protection Agency (EPA) has issued revised procedures for testing various engine categories. This common set of test requirements is set forth in 40 CFR part 1065 and is intended to streamline laboratory efforts, beginning in 2007, for both the EPA and industry and provide a basis for internationally harmonized test procedures for nearly all categories of engines.
The laboratory testing procedures set forth in part 1065 determine brake-specific emissions for duty-cycle testing using an engine dynamometer. This typically consists of one or more test intervals, each defined by a duty cycle, which is a sequence of speeds and torques that an engine must follow. The EPA is also adopting a requirement that manufacturers of heavy-duty highway engines use ramped-modal testing to show that they meet steady-state emission standards using the Supplemental Emissions Test (SET). Much like the part 1065 procedures, ramped-modal testing becomes mandatory in the 2010 model year. Ramped-modal testing involves a single, continuous emission measurement as the engine operates over the test modes in a defined sequence, including short transition segments between modes.
Regardless of the specific test procedure, it is imperative that the various constituent components of the exhaust gas be accurately collected and measured. Particulate matter (PM) is typically collected on a new fine-mesh filter that has been tare-weighted and loaded into a clean filter cartridge. The loaded cartridge is then placed in a test fixture connected to at least a representative portion of the exhaust gas stream produced by the test engine. During the test, PM is collected on the filter during engine operation over a specified duty cycle. The filter is then removed from the test fixture and weighted. The difference between the initial tare weight and the after-test weight is the mass of the collected particulate matter.
Heretofore, the test fixtures used to house a filter cartridge during a test have been containers, such as clamshell or hinged holders that are loaded and moved to a test chamber where they were connected, or plumbed, into all or a predefined portion of the engine exhaust gas stream. These fixtures were cumbersome to use and time consuming to connect. Typically, the exhaust gas flowing through the test fixture is diluted with air to reduce the flow stream temperature. Prior to a test, the test fixture is heated to a prescribed elevated test temperature, for example 47° C., and maintained at that temperature throughout the test. Accordingly, the individual installing or removing the filter cartridge had to use extreme caution, or use special handling tools to prevent burn injuries. The use of gloves when handling a test cartridge is discouraged because of potential contamination of the sample media.
The present invention is directed to overcoming the problems associated with loading, housing and removing filters used a sample collection media in particulate matter engine emission testing. It is desirable to have a test fixture for collecting particulate matter that can be preinstalled as an integral component of a laboratory testing system. It is also desirable to have such a test system that has a sealable filter containment chamber that is readily accessible for installing, sealing, and removing a sample collection filter without connection or disconnection with a laboratory testing system. Moreover, there is a need for a test fixture for collecting particulate matter discharged in the exhaust gas from an engine that does not require extensive cooling time or the use of special handling equipment to remove the test fixture or the filter collection media after a test.